M8000—Power-on has been ON mark
M8001—Power-on has been OFF flag
M8002—Power-on ON one scan cycle mark
M8003—Power-on OFF one scan cycle mark
M8005—PLC backup battery low flag
M8011—1ms clock pulse
M8012—100ms clock pulse
M8013—1s clock pulse
M8014—1min clock pulse
As long as the PLC is RUN, it is considered to be connected. It is generally used to drive the program that runs on power-on!
There are also some instructions in Mitsubishi (especially the rules in the sequence function diagram), some things can not be placed directly with the left bus.
The m8000 is used to achieve direct intersection with the left bus, and does not delay the normal operation of the program. M8000 When your PLC RUN is running, it is turned on. It is the flag. The function of PLC operation is generally applied to the starting point of the bus.
Here, I will see the part of the sequence function diagram.
Of course, most of what you can see is the program that is used to drive the power to run, or the program that needs to run when plc is running normally. Because some errors will stop plc, although the plc has electricity, the program can not run.
PLC M8000-M8990 is a special internal relay of Mitsubishi PLC.
M8000 is a special auxiliary relay. m8000 is always closed during operation. m8001 and m8002 are initialization pulses. When plc is just started, it closes a cycle, but 8001 is normally closed, 8002 is normally open, m8011, 8012, 8013. It is a time pulse with periods of 10ms, 100ms, 1000ms (one second), m8020, m8021, m8022, which are standard real bits, representing benefits, zeros, and endings.
There are other special auxiliary relays, which are commonly used. If you want to know more, you need a programming manual.
M8000-Operation monitors normally open contacts, and the PLC is always ON when it is running.
M8001-Operation monitors normally closed contacts, and the PLC keeps OFF when it is running.
M8002 – Initialize pulse normally open contact, ON one scan cycle when PLC is running.
M8003 – Initialize pulse normally closed contact, OFF one scan cycle when PLC is running.
M8011, M8012, M8013, and M8014 generate clock pulses of 10ms, 100ms, 1s, and 1min, respectively.
Special auxiliary relay.
(2) Coil type. The PLC performs a specific action after the coil is driven by the user program.
M8033 – If its coil is energized, the output image memory and data register contents are maintained when the PLC is stopped.
M8034 – If the coil is energized, the output of the PLC is completely disabled.
M8039 – If its coil is energized, the PLC will operate according to the scan time specified in D8039.